In the case of power failure or a disturbance it could happen in an elevator installation that the passengers in an elevator cage have to wait in darkness for help. In order that this does not occur an emergency light unit, which can provide to the passengers a minimum amount of light, is installed in the elevator cage. This emergency light unit comprises, for example, batteries, capacitors, etc., and is thus, in case of need, independent of the power supply of the elevator cage. It is activated in that a drop in voltage or current is detected. For this purpose the emergency light unit usually comprises a corresponding switching or control unit which detects voltage or current drop and activates the emergency light unit.